US (United States): US version uses US radio frequency from 902 to 928 MHz (on units equipped with wireless transmission) and a 0.01" rain collector. Station reports in US standard units. Includes US power adapter.
USM (United States, metric): US/Metric version uses US radio frequency from 902 to 928 MHz (on units equipped with wireless transmission) and a 0.2mm rain collector. Station reports in Metric units. Includes US power adapter.